Rontgen-ray device



Nov. 1, 1927. I 1,647,614

R. FURSTENAU 1161mm: RAY DEVICE" Filed May 29 1922 FIG.'1.

INVENTOR:

Fatented Nov. 1, 1927.

UNITED STATES remit PATENT OFFICE, 3

ROBERT rt'instrnnau, or BERLIN, GERMANY, ASSIGNOB T-o RADIOLOGIE AKVTIEN- GEsELLsoHArnor nnntrucn aiunnv.

' RClNI'G-EN-RAY DEVICE.

Application filed May 29, 1922, Serial No. 564,391,:51116 in Germany June 6, 1921.

My invention relates to vacuum tubes and more especially totubes operated for the purpose of producingRiintgem-or X-rays.

I follows As is well known to those skilled in the art the heat generated on the anode of Rtintgen tubes in consequence of the impactof the cathode rays is disposed of in the so-called gas containing tubes by embedding the. plate which consists of platinum, tungsten or another suitable material and which serves to receive the cathode rays, in a block of material such as copper or the like possessing a high heat conductivity. In this manner the temperature of the anode plate is kept low even though thetube be ,Worked strongly and fora long time, the anode plate transmitting the heat generated thereon first to the copper block which then further tran inits' it outwards unto air, water or other.

cooling media.

In contradistinction to the tubes mentioned above the vacuum tubes invented by Coolidge and which are devoid of any appreciable contentof gas, embody a new principle of operation as far as the cooling of the anode is concerned, which is designed about as As shown in Fig. 1 of the'drawings affixed to this specification and forming part thereof, in which a Coolidge Riintgen tube is illustrated, the anode (1 consists as awhole of a substan ially cylindrical piece of tungsten, one end of which and which faces the bundle of cathode rays, is as a rule substantially thick and bevelled, whereby a target I) of sufiicient superficial area for the cathode rays is obtained. The heat generated by the oathode rays on the target 1), instead of being transmitted by this anode unto some heat conducting body, is distributed on the tungsten block in such manner that the new contents of heat which are successively transmitted onto it while the tube is operated, will cause its temperature to be raised more and more so that after a few seconds from the start this block will be brought to a white heat. Inasmuch, now, that at such high temperatures as correspond to white heat the radiation of heat increases at a high proportion to the temperature, such anodes will permanently radiate as much heat in form of heat radiation as is conveyed on to them in the operation of the tube. In consequence thereof they will remain in a predetermined v equilibrium of temperature corresponding to rays.

the load and in which the fresh quantitiesof heat conveyed equal the quantities emitted by radiation. v 7

Owing to the fact that the heat is generated substantially in avery small, surface,

the so-called focus, on the forward face of the anode, the load capacity of the tube will be the higher, the shorter the distances between the focus and the heat emitting surface-points. The coolidge anode such as shown in Fig.1, has a relatively small radiating surface, while the distances between the focus and. the heat emitting surface are comparatively great. In consequence thereof in such anodes a very high increase ofheat takes place in the focus itself, the result being, that the cathode rays loosen the structure of the tungsten surface and invade it gradually to greater depth in the direction of the cathode rays so that finally the tungsten block will be destroyed. This action of the rays is extremely favoured by the position of the crystals, the axis of which substantially or completely extends in the direction of the axis ofthe anode and therefore also with the direction of the cathode Obviously the corrosion of the anode greatly diminishes the capacity of the tube and therefore forms a grave drawback for such tubes.

According to the present invention, now, the life and the load capacity of Rontgen tubes-is increased and the drawbacks enumerated above are obviated by l. Thecathode rays being caused to heat the anode surface not in the direction of the axis in which the crystals are positioned in the tungsten, but at an angle to this axis, thus greatly diminishing and in many cases even avoiding corrosion;

2. The distances to be covered by the heat flowing off the focus until it reaches the radiating surface, being materially shortened this heatemitting surface are at the same time enlarged.

This double problem is solved in accordance with the present invention in that the anode consists of a flat plate made in onepiece with the tungsten rod and the crystals of which being positioned to extend in the plane of the plate by any well known mechanical treatment such as rolling the material in one direction more extensively direction in which the material is rolled. The point of contact of the tungsten rod with the plate, instead of being arranged in the middle of the plate, is preferably shifted to its edge.

Three modifications of the anode embodying my invention are illustrated in perspective views in Figs. 2-4 on the drawings.

Referring first to Fig. 2, rear portion a of the tungsten rod is cylindrical after the manner of the'rod shown in Fig. 1, but its forward end which extends in the direction of the cathode rays, merges into a broad plate or surface (Z. This plate is bent so as to extend at an oblique angle to the cylindrical portion a and its forward surface serves for the reception of the cathode rays inasmuch as the position of the crystals is effected in the longitudinal axis of the tungsten rod 0. Obviously the crystal structure in the plate-shaped prolongation (Z will enclose an angle with the direction of the cathode rays as indicated by the arrow I in Fig. 2. By thus shaping the anode I obtain on the one hand a large radiating surface situated a small distance from the focus which offers special advantages for the distribution of heat and for the heat emission by radiation. On the other hand, the oblique position of the crystal structure with regard to the direction of the cathode rays prevents the corrosion of the cathode to take place.

In the construction of the anode it has been ascertained that owing to its flat-shape radiations will arise on its rear side which are so directed as to tend to converge towards the glass wall of the tube which will be overheated thereby. This drawback is avoided in the manner shown in Fig, 3 where a protective plate 7 is disposed to the rear of the anode.

The same effect can be obtained by doubling the broad, plate-shaped portion of the anode about in the manner shown in Fig. I, thus causing the doubled-up portion f to act itself as a protection against reaction emitted from the rear surface of the anode.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled in the art.

I claim: r

1. A Rontgen ray device including a tube at extremely high vacuum with a pure electron discharge, and an anode in the form of a flat plate extending in the direction of emission of the electrons, said plate being doubled up so that the free end thereof extends across its rear surface.

2. A Rontgen ray device including a tube at extremely high vacuum with a pure electron discharge,'an anode in the form of a flat plate extending at an angle to the direction of emission of the electrons, the crystals of said plate extending in the plane thereof, and a protective body extending across the rear surface of said anode.

In testimony whereof I aflix my signature.

DR. ROBERT FURSTENAU. 

